The present invention relates to a method and apparatus for applying self-adhering protective film to vehicle bodies for the protection of vehicles, in particular during the transport thereof.
In the series production of many vehicle manufacturers, the vehicles have to be prepared for despatch in such a manner that they do not become damaged, in particular in such a manner that the paintwork is not impaired by transport and effects of the weather. If journeys by train or even transport by ship are necessary for the transfer to the customer, the vehicles have been covered for this purpose with a wax protective layer which has to be removed again before delivery to the customer. The residue-free removal of the protective wax has not only been personnel-intensive work, but also had an impact on health and the environment because of the solvents used in this case. Moves have, therefore, been recently made to protect the vehicle bodies during transportation by means of self-adhering films; however, only the essentially horizontally lying surface portions of the vehicle body which are at risk from the weather and deposits have been protected in this manner. Because this type of protection is not only very effective but also relatively expensive, this type of protection has not only been provided as protection during transportation, but also as protection during the vehicle assembly and, accordingly, the protective film has already been applied prior to the final assembly of the vehicle, i.e. directly after painting the vehicle body.
The protective film is to be applied in a manner which is as free as possible from folds and bubbles, because under folds or bubbles, after a certain storage time, a micro-climate can form which, depending on the type and colour of the paint, can lead under some circumstances to visible streaks. In order to be able to apply the protective films carefully, the film blanks have previously had to be held by four people, brought over the vehicle, aligned and placed onto the associated surface portions. Despite the high outlay on personnel, it has not always been possible to avoid folds or bubbles during application of the protective film. During the subsequent cutting free of the regions for add-on parts, the paintwork frequently suffered damage requiring costly refinishing work. The procedure for the previous, manual application of the protective film is as follows: first of all, a rectangular piece of protective film, which is matched in terms of size to a surface portion, is pulled off and cut from a supply roll by at least two people, a total of four people having to pick it up. This protective film piece was stretched out freely by the four people using their free hands with the self-adhering side pointing downwards, brought over the vehicle body in this manner and lowered there in a horizontal position onto the associated surface portion in a positionally correct manner, then placed on in a more or less fold-free and bubble-free manner and pressed on by brushing with a soft, slidable object, for example a stiffened piece of felt. In the region of gaps to adjacent vehicle body parts, such as mudguards or doors, which have been glued over, the protective film was cut through manually with a knife and the cut edges pressed on by hand. In order to be able to cut free and cut out the protective film in a manner correct for assembly in the region of add-on parts, such as roof decorative bars, sliding-roof covers, radiator mascot, washer nozzles for windows, aerials, window frames or the like, during the manual film application a flat strip-shaped template has previously been placed in a positionally correct manner onto the vehicle body and this template has likewise been glued over with the protective film to be applied, so that at the regions which are to be cut free the film has not only been held at a small distance from the vehicle body surface, but, by means of the template, a cutting and guide edge for a knife is also formed, along which edge the film can be separated in a contour-correct manner. Working with a sharp-edged knife in close proximity to the painted vehicle body surface has, in the hectic rush, despite continuous practice, time and again resulted in damage to the paint and in costly refinishing work.
This prior art corresponds at least to the manufacturing practice of the applicant; since, for environmental protection reasons, the United States no longer permits protective waxing for vehicle despatch, other vehicle manufacturers are probably turning to a similar film protective system for their vehicles during despatch. However, a prior publication concerned with this is not known to the applicant.
In German Patent Application 196 42 831.9 of Oct. 17, 1996, the applicant describes a method and an apparatus for applying protective film to bodies of passenger vehicles in which, for the purpose of automating the application of the film to the vehicle body, a rectangular piece, of predetermined size, of a protective film from a supply roll is grasped, on the non-adhering side, using a robot-guided clamping-frame, and is pulled off and cut from the supply roll. Before the film blank is placed onto the vehicle body, in the freely stretched-out state, tear-off lines are perforated, from the non-adhering film side thereof, in the region of add-on parts by means of a heated indenting disc, guided mechanically along defined contour lines. Only then is the protective film which is prepared in this manner and is stretched out in a fold-free manner in the clamping frame lowered by the handling robot onto the associated surface portion in a positionally correct manner and placed on in a bubble-free manner. The film is then pressed on with a brushing strip. Since, during and after the application of the film, the clamping frame requires a certain working space in order to apply the protective film in a manner which is as free of bubbles and folds as possible, and since it executes certain pivoting movements, it is only suitable for use for applying films to freshly painted body shells. Using the described clamping frame for the application of films to ready-fitted vehicles is only possible to a severely limited extent, since various fitted parts, for example the windscreen, external mirror, aerial, radiator mascot, etc., restrict the required working space and adversely affect the necessary pivoting movements of the clamping frame. Furthermore, the application of the film using the described clamping frame before the assembly is followed by a manual working step in which protruding, pre-perforated film sections have to be removed. However, in the case of the finished vehicle it is often not possible to place relatively large, protruding film piece onto the corresponding vehicle region, and subsequently to tear off the protruding film along perforation lines, since the protruding film parts, even as they are being placed on, can become stuck to the add-on parts, or, because of the restriction in the clamping of the film, the entire placing-on can be prevented by the add-on parts. Therefore, where required, first of all a relatively small, non-protruding film piece is placed onto the vehicle body. After that, the free regions which are not yet covered are taped down with film strips.
Taking this as the starting point, the invention is based on the object of providing a method and an apparatus for the application of protective film to vehicle bodies, which method offers the user greater flexibility. In particular, it is the aim of the invention, along with more substantial automation, i.e. saving on labour, to propose a method and an apparatus which can be used irrespective of location, both for applying film to painted body shells and also to ready-fitted vehicles.
According to the invention, the film which is to be applied is provided in the form of at least one supply roll in a film-readying apparatus. For this purpose, the film is held in the stretched-out state between two holding elements, preferably suction rails. Within this stretched-out film piece, contour lines along which corresponding film parts can be pulled off again can be perforated in the film using a perforating tool. This may also be required in the case of the finished vehicle, in order to expose, for example, washer nozzles, so that their complete functioning is ensured during the transfer journey.
The perforating tool preferably has at least one heated indenting disc, which is suspended in a floating manner. Alternatively, the perforation can also be carried out using heated gougers or using a laser.
The perforating tool can be guided by different components, for example, SCARA-robots, bent-arm robots or X-Y moving units.
According to the invention, the film which is to be applied is pulled off in a film-readying station from a supply roll to a predetermined length by at least one industrial robot, using at least one holding element, preferably a suction rail, and is held in a stretched state in a waiting position. The film piece held stretched in this manner is picked up at the rear end of the pulled-off film piece by at least one further industrial robot using at least one holding element, preferably a suction rail. The stretched-out film piece is then cut off from the supply roll and subsequently applied to a vehicle body.
After the application of the film, in the same or a further station, using at least one industrial robot with at least one taping down tool, film is applied in the form of film strips to body parts which are still free and which have not yet been covered by the previously applied, rectangular film sections. Furthermore, in this station edges of the applied film which are exposed to the wind are taped down by means of securing adhesive tape. Subsequently, joints and beads of the bodywork which have been glued over by the film are cut free.
By means of the transfer according to the invention of the film to be applied using two holding elements, preferably suction strips, aligned parallel to each other and acting on opposite film ends, an automated application of the film to ready-fitted motor vehicles is made possible, since a rigid clamping frame surrounding the entire film piece is no longer provided, which clamping frame, because of its working space or its pivoting movements, would have to dip, for example, into a region occupied by the windscreen in the finished vehicle. For the handling, by means of two suction strips, of the film section which is to be applied, the suction strips can be moved along with the film held by them, over the vehicle body section to which the film is to be applied, and by uniform lowering can apply the film to this vehicle body part. In the process, the suction strips are guided in such a manner that during the lowering of the film onto the vehicle body part they are guided past next to this vehicle body part, while the other two edges of the film are exposed.
In order to enlarge the working space for the robot-guided perforating tool, the robot-guided holding elements for the film, and also the robot-guided taping down tool, the industrial robots are preferably placed on linear axes. In an advantageous design, for this purpose a linear axis extending over a number of stations can be used per vehicle side, all of the robots of the corresponding side sitting on the said linear axis, on their own moving slides in each case. As a result, the work can be distributed both concentrated to one station in each case and also over a number of stations, for the purpose of optimizing the cycle time.